This invention generally relates to an air conditioner which comprises a single outdoor unit and a plurality of indoor units and, more particularly, to an inverter-aided multisystem air conditioner with control functions of refrigerant distribution and superheating states.
A recent trend in the air conditioning systems mainly used in small and medium size buildings is to use a so-called decentralized air conditioning system in which many air-cooling type air conditioners of a relatively small cooling capacity are installed in the required locations of a building in a decentralized manner. As the result of progressive improvements of this type of air conditioner system, some large buildings have also recently employed such air conditioner systems. However, the use of such air conditioning systems in large buildings involves some problems. For example, since many air conditioners must be installed, much space is required. It is difficult to find enough space for installing the outdoor units of the air conditioners. Additionally, the refrigerant piping with many pipe connections is complicated and difficult to install. To cope with this problem, multisystem air conditioners have recently been proposed for building use. The proposed conditioners have simple and easy piping installation and many improved functions. Hence, many buildings have begun to employ this type of air conditioner. The proposed air conditioners are featured by:
(1) Space-saving installation requirements for the outdoor units, PA0 (2) Few restrictions in refrigerant piping (length and head), PA0 (3) Good controllability for the indoor units, PA0 (4) Individually controllable air conditioners for each segmented room and each zone. PA0 (1) A limited cooling capacity (cooling ability) of the indoor unit, PA0 (2) An inability to coordinate the individual operation of the air conditioners in an economically optimum mode according to the overall air conditioning load conditions. PA0 (3) It is difficult to optimumly operate the air conditioners having different air conditioner load conditions in the air conditioning system of the building. To cope with this, the cooling capacity of the air conditioner system is set to a value slightly larger than that required for the actual use. PA0 U.S. Pat. Ser. No. 923,643 PA0 Filing date 10/27/86, PA0 Title: "Multi-Type Air Conditioner with Optimum Control for Each Load U.S. Pat. No. 4,720,982".
These features greatly contribute to the popularity of the decentralized air conditioners. To attain an ideal air conditioner system, however, there are still many problems to be solved:
To solve the above problems, the following copending patent application has been filed, which has been assigned to the same assignee as that of the present patent application, and whose inventors contain one of the inventors in the present patent application:
This prior patent application will be described in brief.
A microcomputer of the multi-controller is used for controlling both the refrigerant and the electrical systems. Another microcomputer is used for each of the indoor and outdoor units, as in the ordinary inverter air-conditioners.
In the system operation, the microcomputer of the indoor unit first detects the present difference between room temperature and a desired room temperature as preset by the operating unit (of remote control type), and calculates a necessary cooling capacity, and determines a corresponding operating condition, and sends operation commands for start/stop, cooling/heating mode, and operating frequency, which are prepared on the basis of the determined operating condition.
The microcomputer in the multi-controller compensates for the varied cooling capacities of indoor units on the basis of the operating frequency commands from the respective indoor units, and computes the necessary cooling capacity for the overall system, and determines the optimum compressor capacity (inverter output frequency), and sends it to the outdoor units.
In response to the command of the optimum compressor capacity, the outdoor unit operates the compressor at the compensated operating frequency. In the refrigerating cycle of the multi-controller, an open factor of the motor-operated regulating valve of each indoor unit is controlled in proportion to the compensated operating frequency, to regulate an amount of circulating refrigerant.
Thus, the prior art can effectively control the distribution of refrigerant according to the air conditioning load.
There is a demand for further improving the prior art to realize a reliable control for the decentralized air conditioning system by effectively controlling the superheating states of refrigerant.